1. Technical Field
The present invention relates to the technical field of medical devices, and in particular to the technical field of intravascular ultrasound imaging devices used for interventional diagnosis and treatment.
2. Related Art
Intravascular ultrasound tomography (IVUS) is a novel diagnostic method combining a non-invasive ultrasonic diagnosis technology and a minimally invasive technology of interventional catheterization. As IVUS may accurately present a complex 3D anatomical structure of a blood vessel wall in real time, in addition to evaluating stenosis of lumen, it may further detect vulnerability of an atherosclerotic plaque and load of the plaque. Therefore, in the percutaneous coronary intervention treatment, IVUS has gradually replaced coronary angiography (CAG) that is originally deemed as a “gold standard” for diagnosis and treatment of a coronary heart disease, and becomes a novel diagnostic method widely applied clinically. The operation principle thereof is that, a small-sized ultrasonic transducer is installed on top of a flexible catheter about 140 cm long and about 1 mm thick, and the IVUS catheter is sent to a remote side of a target lesion location through a guide wire; during a process of pulling back the catheter (at a pullback rate of 0.5 mm/s), the ultrasonic transducer conducts 360° scanning around a blood vessel within a cavity of the blood vessel, and meanwhile, sends and receives high-frequency ultrasonic signals within the blood vessel, to implement cross-sectional imaging for each layer of the blood vessel wall, thereby assisting clinical doctors to give diagnosis for a coronary artery lesion. As a result, an intravascular ultrasound instrument includes three main components: 1) a catheter equipped with a micro ultrasonic transducer; 2) a pullback apparatus; and (3) a computerized ultrasound device with image rebuilding software and hardware. Undoubtedly, the catheter (i.e. ultrasound probe) equipped with the micro ultrasonic transducer directly operating within a narrow coronary artery is the core component that has the highest technical intensity in the entire intravascular ultrasound machine. The performance thereof directly affects quality of images and a signal-to-noise ratio, and also decides functions of system equipment and safety of use.
A commercialized intravascular ultrasound (IVUS) probe, according to structure thereof, may be roughly classified into 2 types: a mechanically rotating probe and an electronically scanned array probe. The electronically scanned array probe includes multiple (64 at most so far) array elements which are arranged in a ring shape on top of the catheter, to obtain a 360-degree cross-sectional image through sequential excitations by an electronic switch. The advantages thereof include that, neither a rotating part nor a conducting wire for connecting a single crystal is used; the guide wire passes through a central cavity thereof and easily passes through a target lesion; and it is not required to inject any liquid during use. However, there are disadvantages such as a lower image resolution and a 1-2 mm2 ultrasonic dead band easily occurring around the catheter. Although using more array elements may improve the imaging resolution, in the meantime, it will increase the volume of the probe, thus severely affecting application thereof as the intravascular probe. The mechanically rotating probe, may be further classified into 2 types, including a rotary reflector type probe (i.e. the transducer does not move but the reflector rotates) and a rotary transducer type probe, both of which are rotated (at a rate of 1,900 rpm) by a flexible driving rotary shaft within the catheter to obtain a 360-degree 2D cross-sectional image. Within a catheter of a single mechanical sector probe, gap between the transducer and a catheter sheath needs to be filled with a physiological saline solution, to achieve the best acoustic coupling. The type of mechanical sector probe, compared with the electronically scanned array probe, is advantageous in a higher imaging resolution, but the greatest disadvantage thereof is, when the catheter passes through a lesion with high-grade stenosis or a blood vessel section being curved, a friction may occur between a main shaft of the probe which is conducting rotary scanning and an inner cavity of the catheter to a great extent, thus obstructing free rotation of the catheter and causing rotation distortion to the image.
In addition, existing commercialized IVUS catheters may only help the doctors see an image of the blood vessel wall on a side of the ultrasound catheter, but fail to present an image of the blood vessel in front end thereof, such that their use is much restricted in Chronic Total Occlusion (CTO) lesions. As the most difficultly conquered problem in coronary arterial and peripheral arterial intervention treatment, CTO has a very high proportion among peripheral arterial diseases. A successful technology on blood vessel patency is the highest point of the intravascular interventional technique and CTO lesions have always constantly inspired wish of numerous clinical doctors to conquer them. The difficult problem of CTO in the medical field urgently demands research and development of forward-looking IVUS (FL-IVUS). It may be predicted that, a forward-looking IVUS catheter integrated with a radiofrequency ablation electrode may achieve visual stepwise ablation of a plaque within a partly or completely occluded blood vessel, and will provide a bright lamp for doctors performing an interventional operation, to give them the most “accurate” thoughts and therapies. Therefore, it has very broad application potential and great research significance.